DESCRIPTION: The most common cause of failure of all forms of intervention on the arterial and venous side of the circulation is myointimal hyperplasia. It represents the response of the vascular wall to injury. The injury is a complex phenomenon involving the endothelium and smooth muscle of the media. when initiated, smooth muscle growth along with the deposition of matrix leads to narrowing of the vessel, which may in the extreme case, lead to thrombosis and failure. The most common site for this to occur in the peripheral arterial circulation is in saphenous vein grafts that have been placed to bypass areas of occlusion. The incidence of this is in the range of 20-40%. the purpose of this proposal is to develop sensitive quantitative methods for graft surveillance with the goal of detecting lesions before failure of the conduit occurs and when intervention will preserve the long-term function of the graft. The proposal is designed to develop and evaluate ultrasonic methods that can be used to generate three dimensional models, as well as high resolution images of the lesions themselves. In addition, by the use of high resolution ultrasound, it is proposed to test the role of the intima-media of the vein graft in preventing proliferation of the smooth muscle. The target population will be those patients who have undergone saphenous vein grafting and who can be followed at frequent intervals during the first year, which is the time in which these problems develop. At each visit, studies of flow velocity, geometry and three dimensional reconstruction of the vein graft will be carried out. for all detected lesions, their progression/regression will be monitored by these techniques. Intervention will only be done when the lesions within the graft lead to the development of a pressure gradient or symptoms return. In addition, it will be possible to monitor the status of atherosclerosis in the inflow and outflow arteries to assess its role in graft function and outcome. This is the first study designed to provide natural history data on this lesion, which is such a common cause of failure in the arterial system.